rsbob 

Tell me if extreme heat or cold is more detrimental to your average speed compared to a nice Spring day. I am not talking about moving to a fat tire snow bike in the winter, but riding the same route on your regular bike when it is blisteringly hot or super cold. If you keep stats, you can cheat and look back.

Mr Robot says, “Cold weather can pose challenges to athletes but also burns more calories. The body needs to work harder to perform in a harsher climate and generate adequate heat to keep warm . Cold stress can have a potent effect on performance, and the minimum temperature value is more important for cold weather sports due to the impact of cold stress.Exercising in hot weather can also have both positive and negative effects on sports performance. Heat acclimatization can improve athletic performance in warm-hot environments, especially for aerobically trained athletes . However, hot and humid environments can have deleterious effects on athletic performance. Increased temperature has been correlated with decreased athletic performance due to excessive fluid loss, impaired thermoregulation, and other factors.”